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Why do we use only blue or black ink?

Lately, I’ve been wondering why we predominantly write with pens that have inks in two colours: blue or black. I remember that in school we were explicitly told not to use green, purple, or heaven-forbid, red pens. The penalty was death. I’m kidding, the teachers only caned us.

I remember that the school principal used to use a green coloured pen to sign letters or late slips or whatever. That green seemed exotic at the time.

I think teachers didn’t want you to write in red because they evaluate answer sheets with their own red pens and the colour clash can lead to confusions.

What I don’t get though is why we’re asked not to use any of the other colours. Green is a perfectly fine colour to use, so is violet, maybe even brown. I’ve never tried the latter two, so I don’t know.

I did buy red and green refills a few weeks ago and I started using the green one, but I had to change to blue. I was afraid that someone would use the green pen without knowing and accuse me of ruining a cheque leaf or whatever else.

Which brings me to my second point. I get why schools — whose job it is to get you ready to conform — would restrict the colour of pens that you can use. Why is there the same restriction in the real world? A form that I came across recently had instructions that told you to use blue ink only. And, in my various forays into the real world, corporate or otherwise, I can’t remember a single time that I’ve seen a pen with green or a purple coloured ink being used. I’m not kidding.

I can make a case for not using red because it’s associated with danger (traffic signal for example) but why not green or any of the other reasonably dark colours? I’m not asking for yellow and pink pens because I think that they’ll be hard to read on white paper, but brown, purple, green, maroon — they’re all colours that can be read.

If you know the answer or have a theory about why we use only specific coloured inks, feel free to chime in. I’m stumped.

Some research after the fact

After I finished writing this post, I went to Google and found this article. It explains why blue ink is preferable on legal documents — it contrasts with the black print. Another point made, in a different place, was about copiers and scanners and how certain colours don’t copy or scan well.

Interestingly, there’s a lot of discussion on this topic but I haven’t come across any definitive answers.

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12 thoughts on “Why do we use only blue or black ink?”

When I was training to be an accountant (in England) we were taught that only auditors may use green ink. This was before everything was done on computers. if you saw notes in green ink on accounts you knew they had been examined by an auditor.

Too lazy to research this :), but I’d say that black ink would probably have been the easiest and cheapest ink to make that also offered the highest contrast on white (which is we still use it on screen). You could make it from things like soot, lampblack, tar, etc.

So it’s really blue ink that’s the conundrum.

Another possibility is that black and blue inks from that time lasted longer.

@Suchi: Fascinating theory about why we use blank ink. After reading your comment, I realized that a part of the point that I was making was that we may be doing this out of historical reasons and our ink choice may have nothing to do with the present.

Purple ink was used in French schools in the Napoleon days, not sure if it started before or after though, still carries to this day. (their blue ball pens have more purple than american counterparts) Also red ink is outlawed, because the colour was deemed “too aggressive” for school. (even from teachers)

I remember that in China, before the 2000s, students were still mostly using fountain pens, we were only allowed to use blue ink and not black, because answers written in black would get confused with exam questions, which were handwritten by teachers and then plated.

I went to school in Germany in the 80s. Red ink was used by the teacher and green ink by the principal. Those two inks were prohibited for student use.

Most students used blue ink (fountain pens with cartridges), because the blue ink can be erased chemically, that doesn’t work that well with other colors. Black would have been ok as well, but some people used other colors from brown to violet.

Believe it or not, but in these days the administration still uses colored pens to denote hierarchy. Green for ministers, red for directors. Violet and brown designate two steps down the hierarchy.
Peons can choose between blue and black.

Official signatures are either black or blue. Black ink has the advantage of aging stability (blue fades), but if you sign a job application in black, they might throw it away immediately, because it cannot be distinguished from a photocopy.